In semiconductor manufacturing machines, fluids such as clean-air, purified water, temperature-controlled water, organic chemicals and the like are used. Resin tubes, such as fluororesin tubes, polyurethane tubes, nylon tubes and the like, are used as pipes for carrying these fluids, and stainless-steel fittings are used as fittings for connecting these resin tubes, taking into consideration oil content and impurity countermeasures. Currently, double ferrule-type stainless-steel fittings are heavily used as fittings for resin tubes.
In the Non-Patent Reference 1, below, a pipe fitting, which comprises a fitting main body having an insert part, a sleeve which is provided movable on the outer-side of the insert part, and a nut which screws onto the fitting main body and moves the sleeve, wherein a protrusion part is provided on the outer-side of the insert part, the pipe is inserted into the insert part, the nut is screwed onto the fitting main body, and the sleeve is moved to the outer-side of the protrusion part and presses and locks the pipe fitting, is described.    [Non-Patent Reference 1] Nitta Moore Company pamphlet, “Chemifit CS Series”